Growth and maintenance respiration of leaflet, stipule, tendril, rachis, and petiole tissues that make up the compound leaf of pea (Pisum sativum)

Abstract

Respiratory changes during development, as well as growth and maintenance coefficients, were measured in organs of a typical compound leaf at the seventh node position of a pea (Pisum sativum) plant. The leaf consists of both laminar (leaflets and stipules) and cylindrical organs (tendrils, rachis, and petiole). Young tissue of each organ had relatively high respiration rates that declined as the tissue expanded. The respiration rates of leaflet, stipule, and tendril tissue throughout maturation were significantly greater than those of the other organs. The growth respiration coefficients were not significantly different among laminar and cylindrical organs. Maintenance respiration, expressed on a total dry mass basis and on a carbohydrate-corrected dry mass basis, as well as in vitro photosynthetic rates, were significantly lower in petioles and rachises than in tendrils or the leaflets and stipules. No difference in maintenance respiration of organs was observed when rates were expressed on a protein basis. A linear relationship between mass-based respiration and organ protein concentration was observed, suggesting that the energy costs involved in protein turnover may account, in part, for the differences in maintenance respiration among the organs. Taken together, our data show that although the tendril is structurally similar to the rachis, petioles, and stem, which have a role in supporting the canopy of this climbing plant, the respiratory properties of tendrils are more like those of leaflets and stipules, thus parallelling the photosynthetic characteristics of these organs in the compound leaf. Keywords: development, leaflets, Pisum sativum, respiration, stipules, tendrils.